National Consultation with TNMC3 May 2005, Bangkok

WUP-FIN Phase II – Bank erosion study

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Vientiane bank erosion

~ 30 km long part of the Mekong

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Tools

The EIA 3D hydrodynamic and basic sediment model

New developments for sediment modeling (sediment fractions, bed load, refined erosion and sediment transport description, bank erosion potential calculation)

Bank erosion model

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Model inputs

River and floodplain topography• Hydrographic atlas data • river cross-sections, • digital elevation map (DEM) for floodplain

Boundary conditions• Upstream discharge and water level• Upstream sediment concentrations (sediment fluxes)• Downstream rating curve (at Nong Khai)• Downstream sediment concentrations

Landuse Bed and bank material characteristics Wind

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Hydrographic atlas data

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Model interface for pilot model

EIA 3D model system

Hydrodynamic Sediment

transportation

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Existing data

Mekong River Commission River topography from the digital Mekong

Hydrographic atlas River bank location from the Mekong Hydrographic

atlas in early 1990s Hardcopy of old Hydrographic atlas from 1960s Digital elevation map for the land area with 50 m

resolution from old topographical maps and new SRTM elevation model with 90 m resolution

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Existing data

Lao PDR Historical TSS concentration measurements at

Vientiane port Daily water level and discharge in Vientiane port Bed changes during time have been measured in two

projects: JICA (2004) and bank protection project in 1988

Aerial photos from 1991 of Mekong around Vientiane and Nong Khai

Thailand Daily water level and discharge in Nong Khai

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Existing data

International Bank material analysis made by JICA (2004) and

Miazawa et al. (2004) Bed material analysis made by Miazawa et al. (2004)

and JICA (2004) Velocity profile measurements on Laos side on three

sites done by JICA (2004) Analysis of the bank erosion in Vientiane area made

by Rutherford and Bishop (1996) with some mapping comparing the old and new Mekong Hydrographic Atlas

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Data request from TNMC

Hydrology Hourly WL data from Nong Khai station (all the available

years) Water level data in other places than Nong Khai inside the

modelling area Data from ADCP runs at Nong Khai (all the available runs) Other discharge / flow velocity information

Water quality TSS concentration measurements at Nong Khai (all the

available years) Depth integrated suspended sediment concentration

measurements at Nong Khai Suspended sediment grain size analysis Bed load measurements

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Data request from TNMC

Soil and bathymetry data Bank material analysis for Thailand side from model area by

national agencies Bed material analysis for Thailand side from model area by

national agencies Bathymetry data for Mekong from model area (other data

than Hydrographic atlas data)

Other Aerial photos from 1960s of Mekong around Vientiane and

Nong Khai, archived in Bangkok Land use in the river banks, floodplains

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Field data collection

Lateral (morphological) changes in river bank• Comparing the aerial photos and satellite images

SS concentration combined with the ADCP measurements

Cross section changes• Selection of cross sections will be monitored

Longitudinal section changes Bathymetry of the river

• Missing areas from hydrographic atlas• Possible changes during the last 15 years

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Field data collection

Material analysis in river bed and bank Bank profile and landuse Recording current meter

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Direct model outputs

Vertical and horizontal velocity and sediment distributions

Bed shear stresses and bed erosion/ sedimentation

Bed sediment distributions and their changes over time

Bank erosion potential and changes over time Morphological changes

MRCS/WUP-FINwww.eia.fi/wup-fin